The present invention relates generally to classifying objects in an image, and more particularly to detecting whether an adult person, a child or an infant seat is present on a seat of a motor vehicle.
As a safety feature, modern motor vehicles incorporate an air bag inside the dashboard in front of a passenger in the forward seat. Additional air bags are being proposed for the doors to the sides of these occupants. Rapid deceleration of the motor vehicle during an accident is detected and activates inflation of the air bags which cushion the occupants.
Although air bags have greatly decreased the severity of injuries from motor vehicle collisions, people are occasionally injured because of the rapid rate with which the air bag must deploy. In particular, the air bag may severely injure a small child or infant sitting in the front seat of the vehicle.
As a consequence, it is now recommended that small children and infants ride in the rear seat of the vehicle so as not to be exposed to the force of air bag deployment in the event of an accident. However, that does not address the situation which occurs when that recommendation is ignored and a child rides in the front seat of the vehicle. Furthermore, in vehicles that do not have a rear seat, such as sports cars and trucks, a child or infant must be placed in a seat that faces an air bag. In this latter situation, it has been proposed to provide a manual override switch to disable the air bag in front of the child. However, not only must this switch be manually operated whenever a child is present, the motor vehicle operator must remember to re-activate the air bag for adult passengers.
These precautions also do not address the presence of a relatively small adult occupant in a vehicle with an air bag designed to protect an larger person. Thus there is a need for the air bags to be controlled dynamically in response to whether the person in the motor vehicle seat is an adult, a child or an infant in an special infant seat.
The present invention provides a mechanism for detecting the presence or absence of an occupant on a seat within a motor vehicle and classifying the type of person. The method also distinguishes inanimate objects on the seat from people.
An image of the object is acquired and then segmented into a first segment and a second segment. For example, the object is divided into the segments based on a demarcation line at a fixed position in all images that are processed. The first segment is substantially enclosed by a first geometric shape, such as an ellipse, that is defined by a first set of parameters. The second segment is substantially enclosed by a second geometric shape that is defined by a second set of parameters. The two sets of parameters are combined to form a feature vector that characterizes the object.
The feature vector is compared to template vectors, each representing different class of objects, to determine probabilities that the object falls within each class. In the preferred embodiment, a Bayesian classification technique is utilized to produce the set of probabilities. A class for the object is determined based on those probabilities. For example, the object is placed in the class that has the greatest probability.
However, if none of the probabilities exceeds a predefined threshold value, it is unlikely that the object fits into any of the predefined classes. In that case, the object is considered to be in the empty seat and irrelevant object class.
A process also is described for forming the template vectors for each of the predefined object classes.
The present invention has particular application in controlling an air bag in the motor vehicle. Specifically, this classification method can be used to determine whether the object on the seat is an adult person, child or an infant seat, and whether the infant seat is facing forward or rearward. This classification then is used to control whether the air bag inflates during an accident and if so, the speed of inflation so as to protect the seat occupant from injury by the air bag.